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Dr. Eger Inhaled Anesthesia Lectures (Anes Pharm Exam 3) > Ch3 Understanding Minimum Alveolar Concentration (MAC) > Flashcards

Ch3 Understanding Minimum Alveolar Concentration (MAC) Flashcards

1
Q

What does MAC stand for in anesthetic terminology?

A

Minimum Alveolar Concentration

MAC is the concentration that blocks movement in 50% of patients.

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2
Q

What is the primary mediator of MAC?

A

The spinal cord

This was established through various studies indicating that the brain does not significantly alter MAC.

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3
Q

Why is MAC determined at 50% response rather than 90% or 95%?

A

It provides a more stable and easily measurable value

Determining MAC at 50% minimizes variability and requires fewer experimental subjects.

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4
Q

What physiological factors can affect MAC?

A

Age, temperature, hydration, and certain clinical conditions

These factors can alter central nervous system sodium levels, affecting MAC.

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5
Q

How does nitrous oxide affect MAC?

A

Reduces MAC by about 50-60% for each percent added

This highlights the influence of nitrous oxide on the potency of other anesthetics.

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6
Q

What is MAC awake?

A

The concentration that suppresses response to command in 50% of subjects

MAC awake is typically higher than MAC for amnesia.

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7
Q

True or False: Muscle relaxants significantly affect MAC.

A

False

Muscle relaxants are polar agents and do not enter the brain, thus having no significant effect on MAC.

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8
Q

What pharmacologic agents can synergistically decrease MAC?

A
  • Opioids
  • Benzodiazepines
  • Barbiturates
  • Alcohol
  • Propofol

These agents can enhance the anesthetic effect, allowing for lower MAC levels.

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9
Q

What technique is used to determine MAC in humans?

A

Dixon up-and-down technique

This technique involves observing movement response in pairs of patients to bracket MAC values.

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10
Q

What is the effect of age on MAC?

A

Older age typically requires less MAC

This is due to changes in physiology and drug metabolism with advancing age.

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11
Q

Fill in the blank: The concentration of anesthetic that blocks the adrenergic response in 50% of patients is known as _______.

A

MAC

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12
Q

What is the impact of dehydration on MAC?

A

Can alter central nervous system sodium

This alteration can affect the required MAC levels for effective anesthesia.

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13
Q

What does the term ‘equilibration’ refer to in the context of MAC determination?

A

The process of allowing alveoli and spinal cord concentrations to equalize

Proper equilibration is necessary for accurate MAC measurement.

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14
Q

What is the primary effect of intravenous anesthetics like propofol?

A

Primarily affects the brain, with minimal effect on the spinal cord

This distinguishes how different anesthetic types operate within the central nervous system.

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15
Q

How does temperature influence MAC?

A

Lower body temperature requires less MAC

This is due to the decreased metabolism and altered drug dynamics at lower temperatures.

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16
Q

What is the significance of maintaining low MAC awake levels?

A

To avoid regurgitation and ensure patient safety

High MAC awake levels can lead to complications during anesthesia.

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17
Q

What technique defines neck for inhaled anesthetics in humans?

A

Dixon up and down technique

This technique is used to determine the minimum alveolar concentration (MAC) of anesthetics.

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18
Q

What was observed about the child during the anesthetic induction?

A

The child was calm and cooperative, held the mask to his face, and showed purposeful movement during painful stimulus.

This demonstration illustrates the determination of MAC in a pediatric patient.

19
Q

What is the range of MAC values for humans?

A

0.75% to 1.05%

These values are specific to inhaled anesthetics and vary by age.

20
Q

Does gender affect MAC?

A

No

Gender does not influence the MAC value.

21
Q

List physiological factors that do not change MAC.

A
  • Gender
  • Duration of anesthesia
  • Body mass
  • Height
  • Blood pressure above 50 mmHg

These factors remain constant as long as physiological parameters are normal.

22
Q

How does age affect MAC?

A

MAC decreases with increasing age

Older patients require lower concentrations of anesthetics.

23
Q

What effect does body temperature have on MAC?

A

Lower body temperature decreases MAC

A 10-degree decrease in body temperature can halve the MAC.

24
Q

How does chronic alcohol consumption affect MAC?

A

Increases MAC

Chronic alcohol users may require more anesthetic compared to non-users.

25
What pharmacologic agents decrease MAC?
* Opioids * Benzodiazepines * Barbiturates * Propofol * Nitrous oxide ## Footnote These agents have a synergistic effect on anesthetic requirements.
26
What is MAC awake?
The concentration that suppresses appropriate response to command in 50% of subjects ## Footnote MAC awake is usually higher than MAC for amnesia.
27
How does dexmedetomidine affect MAC?
Decreases MAC ## Footnote Dexmedetomidine can act as an anesthetic itself.
28
True or False: Muscle relaxants affect MAC.
False ## Footnote Muscle relaxants do not change MAC as they do not penetrate the central nervous system in significant amounts.
29
What central nervous system effect can muscle relaxants have if administered directly to the brain?
They can cause convulsions ## Footnote This highlights their potential CNS activity when not used as intended.
30
What is the effect of nitrous oxide on MAC?
Reduces MAC by approximately 1% for each percent of nitrous oxide ## Footnote Nitrous oxide has a significant impact on the anesthetic effect.
31
What happens to MAC when sodium levels in the central nervous system decrease?
MAC decreases ## Footnote Changes in hydration status can affect sodium levels and subsequently MAC.
32
What is the relationship between MAC and the risk of regurgitation?
Higher MAC increases potential for regurgitation ## Footnote Relaxation of the upper esophageal sphincter is related to this risk.
33
What is the significance of the study on isoflurane and nitrous oxide regarding MAC?
It showed differences in appropriate response to command among anesthetics ## Footnote This indicates variability in anesthetic efficacy based on type.
34
What factors affect Mac awake?
Age and anesthetic type ## Footnote Age affects Mac awake; as one gets older, Mac awake decreases.
35
How does Mac awake vary among anesthetics?
It varies significantly between different anesthetics ## Footnote For example, nitrous oxide has a much higher Mac awake value compared to isoflurane.
36
What was the Mac awake value for nitrous oxide?
Above 60% of Mac ## Footnote Nitrous oxide's Mac awake value is significantly higher than that of isoflurane.
37
What was the Mac awake value for isoflurane?
30 to 40% of Mac ## Footnote Isoflurane has a lower Mac awake value compared to nitrous oxide.
38
Why is Mac awake important?
It helps in determining recovery time from anesthesia ## Footnote Faster recovery times can lead to quicker patient discharge from the post-anesthesia care unit (PACU).
39
Which anesthetic would be chosen for quicker recovery?
Nitrous oxide ## Footnote Nitrous oxide is preferred due to its rapid recovery profile compared to potent inhaled anesthetics.
40
What is the Mac of nitrous oxide?
105 ## Footnote This indicates that delivering 70% nitrous oxide leaves a small margin between Mac awake and maximum delivery.
41
What must be done if using nitrous oxide at high concentrations?
Supplement with other anesthetics ## Footnote Common supplements include propofol, sevoflurane, or isoflurane.
42
What is a downside of nitrous oxide?
High Mac awake means it's not a good amnestic agent ## Footnote Patients may still have awareness, necessitating supplemental anesthetics.
43
True or False: Nitrous oxide alone is sufficient to suppress awareness.
False ## Footnote Nitrous oxide requires supplemental anesthetics to effectively suppress awareness.

Dr. Eger Inhaled Anesthesia Lectures (Anes Pharm Exam 3) (8 decks)

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